Field of the Disclosure
The present disclosure relates generally to detection of optical signals and, more particularly, to equalization of optical signals.
Description of the Related Art
Digital signal processing (DSP) is used for coherent (intradyne or homodyne) detection of optical communication signals in optical transport systems. For example, DSP-based detection of coherent wavelength division multiplexed (WDM) optical signals is used for long-haul and metro WDM optical transport networks. The application-specific integrated circuits (ASICs) that have been developed to perform DSP detection of optical signals often require relatively high power consumption, which impedes the development of commercially viable optical transceivers suitable for data rates higher than about 100 gigabits per second (Gbps). Power consumption can be reduced by reducing the sampling rate of the analog-to-digital converters (ADCs) that sample input symbols to produce digital signals that can be processed to recover the information carried by the symbols. For example, reducing the sampling rate of the ADC from two samples per symbol (SPS) to 1.P SPS (where “.P” is a decimal fractional value smaller than one) can reduce the power consumption by a factor of approximately (2-1.P)/2. However, reducing the sampling rate to a value less than 2 SPS introduces aliasing noise into the digital signals because the signal bandwidth can exceed the Nyquist limit. The aliasing noise can be filtered using an analog filter but anti-aliasing filters with analog components can be difficult or costly to manufacture, particularly if the manufacturing specifications for the anti-aliasing filter are stringent.